This invention relates to the rain erosion protection art and the thermal shock protection art and, more particularly, to a unique device for protecting the optical dome of the seeker system of an airborne vehicle, such as a missile.
One of the primary objects of a low cost lightweight missile (hereinafter referred to as "LCLM") is, obviously, the incorporation into the LCLM of low cost components. Hence, the ultraviolet/infrared transparent materials that were considered initially for use as the optical dome of a LCLM were Cortran 9754 (i.e., a tempered germanium doped glass) and quartz, both of which are relatively inexpensive. However, after a more detailed consideration, it was ascertained that both of these materials have limitations for use in the designated flight environment of the missile. That environment includes falling raindrops, and thermal shock at the flight velocities of the LCLM, which are variable from sub-sonic to (and including) supersonic.
For example, Cortran 9754 will begin to be damaged by erosion by the impact of raindrops during flight velocities of between 300 and 600 feet per second, and the rain damage velocity threshold of quartz is less than 400 feet per second. Additionally, quartz will not be affected by the thermal environment, whereas Cortran 9754 is subject to thermal shock, except for very thin configurations. Therefore, unless a solution is found which permits the use of Cortran 9754 and of quartz, substantially more expensive materials, such as magnesium oxide and sapphire, will have to be considered for use as the optical dome material.
I have invented a unique optical dome protection device which is inexpensive, and which will protect erodible materials, such as Cortran 9754 and quartz, from rain damage; and, which will also protect thermal shock-susceptible materials, such as Cortran 9754, from cracking due to the thermal environment. As a result, these and other inexpensive materials can be used with my invention to produce a low cost optical dome which will survive supersonic flights in rain. Therefore, with this invention I have satisfactorily solved the aforesaid existing problem; and, thereby, I have significantly advanced the state-of-the-art.